Use of Methylene Blue in Patients With Shock in the Intensive Care Unit Over a 10-Year Period at a Private Hospital in Costa Rica.

Introduction Methylene blue (MB) has been proposed as an adjunctive therapy for the management of refractory shock; however, clinical evidence from Latin America remains limited. This study evaluated its impact on hemodynamic parameters and clinical outcomes in critically ill patients. Responders were defined as those who demonstrated hemodynamic improvement after MB administration, meeting at least one of the following criteria: an increase of ≥10% in mean arterial pressure (MAP), a reduction of ≥10% in vasoactive-inotropic score (VIS), or a ≥10% decrease in serum lactate levels.  Methods A retrospective cohort study was conducted in the intensive care unit (ICU) of Hospital Clínica Bíblica, a private hospital in Costa Rica, between January 2014 and December 2024. A total of 98 adult patients with refractory shock who received MB were included. Clinical and laboratory variables were assessed before and after treatment. Response was defined as a composite endpoint (≥10% improvement in MAP, ≥10% reduction in VIS, or ≥10% decrease in lactate). Statistical analysis included Wilcoxon signed-rank tests, ANOVA/Kruskal-Wallis, and logistic regression models.  Results The mean age was 72.6 ± 14.1 years, and 65.3% were male. Septic shock was the most frequent etiology (55.1%). Thirty-day survival did not differ significantly across shock types (log-rank p = 0.171), although clinically relevant trends were observed. Overall, 73.5% (n = 72) of patients met the composite response criteria. Significant improvements were documented in the MAP (70.5 ± 19.3 to 74.2 ± 21.9 mmHg; p < 0.001) and shock index (p = 0.003). VIS increased at the population level (median 6.0-21.0; p < 0.001), reflecting heterogeneity in response. Bolus or bolus plus infusion strategies showed higher response rates than continuous infusion (82.9%, 90.0%, and 62.3%, respectively; p = 0.045). Lower pre-treatment VIS was independently associated with higher odds of response (aOR = 0.979, p = 0.016), and higher post-treatment MAP was associated with reduced mortality risk (aOR = 0.933, p = 0.005).  Conclusions MB may represent a beneficial therapeutic option in selected patients with refractory shock. Bolus administration, alone or combined with infusion, appeared more effective than continuous infusion. MAP and VIS may serve as dynamic markers of response, although VIS was heterogeneous and influenced by outliers. Prospective, multicenter studies are required to confirm these findings and identify patient subgroups most likely to benefit.